Color cinematorgaphy



Aug. 17 1926. 1,596,808

D. F. COMSTOCK CGLOR CINEMATOGRAPHY Filed Jan. 5 1922 Patented Aug. 17,1926.

UNITED STATES PATENT OFFICE.

DANIEL F. COMSTOCK, F CAMBRIDGE, MASSACHUSETTS, ASSIGNOB, BY -MESNE AS-SIQNMENTS, T0 TECHNICOLOR MOTION PICTURE MASSACHUSETTS, A CORPORATION OFMAINE.

CORPORATION, OF BOSTON,

COLOR CINEMATOGRAPHY.

Application filed January 5, 1922. Serial No. 527,069.

This invention relates to the .art of color photography, moreparticularly to the socalled subtractive branch of the art. in which thecomplemental images represental tive of the two or more color aspects ofthe object-field are supported in superposed registry incontradistinction to the additive branch where the complemental'imag'esare separately supported'pnd separately pro jected upon a screen 1nregistry, and still more particularly to films adapted to produce colorpictures and to the method of making such films.

In the production of color films of the subtractive type there arevarious ways of making the colored positive. However, those methodswhich involve printing or otherwise forming the positives on separatestrips and subsequently joining the various posizo tives together tomake a multily positive or otherwise usin the separate lms to produce asingle-wi th color film, possess advantages over other methods inasmuchas they avoid the difiiculties incident to carrying multi-wi'dth ordouble-coated or recoated films through the necessary stages.

The resent invention has to do only with the rst-mentioned class of'processes, that is, processes involving the use of separate films forthe respective complemental series of images either when physicallyincorporated in e finished film or where used in the production of same.The following are examples of such processes.

One method comprises forming complemental series of negatives onseparate films, printing separate sitive films from the negativesrespective y and subsequently uniting the positive films with thecomplemental ositives in superposition. A second method iflers from thismethod in that all the negatives are formed on a single film, thenegatives of the respective series alternating longitudinally of thefilm. A third method comprises the formation of master ositives inrelief form, the respective com emental series being formed on separateand thenprinting the master. 'tives in superimbibition.

position u on a blank fi by Q ourth an fifth methods are similar to saidfirst and second methods but the positives are produced in relief formby printing from master positives and etching off the exposed emulsionleaving the unexposed emulsion in the form of indirect reliefs whichconstitute positives, the reliefs of the res )ective complemental seriesare stained di erent colors, and the complemental films are cemented orotherwise joined together. Sixth and seventh methods differ from thelast aforesaid methods in that the positives chines, it has beendilficult to secure proper color' balance between the images of thecomplemental sets when separately printed on separate films. This isevidenced when the finished pictures are projected upon the screen bvariations in the general color cast of t e pictures. For example, thepictures may first have a reddish cast and as the film progresses thismay change to a greenish cast and so on. While this variation isordinarily not of the first order of magnitude it is frequentlysufiiciently pronounced to be decidedly objectionable. Moreover a markedvariation in color may occur at any time and at frequentintervals,regardless of the care exercised in preparing the film.

The present invention is based on the discovery that the aforesaidvariations in color balance are attributable to variations in thecharacteristics (such as sensitivity and sometimesthickness) of theemulsion of the respective films employed in making the finishedpositive, this variation-necessarily occurring in the commercialmanufacture of positive film stock. Variations in the sensitivity of thepositive films (or the master positives) produce variation in the densitor thickness of the develo ed images of eac series of positives througout the length of the film. In addition to this effect of varia:

tion in sensitivity, in the aforesaid indirect method-of'making reliefs,where the ex osed emulsion is etched ofi, variation in the t ickness ofthe emulsion also produces a variation in the average depth of theremaining emulsion constituting the indirect reliefs. Moreover, in theuse of special films in which the light absorptivity is an importantelement, variations in the absorptivity from point to point along therespective component films causes disturbing variations in the colorvalues of the final film.

Inasmuch as these variations in density in each series (optical densitor depth in the case of reliefs) are irregu ar, the net result is theaforesaid variation in general color cast of the projected pictures. Intwo-color films where the complemental series are colored red and greenrespectively, the pictures have a reddish cast where the green film runsunder-dense or the red film runs over-dense and vice versa.

Not only do the separate films varIy individually throughout theirrespective engths are made up of a lurality of sections spliced togetherthis di erence in average necessitates a change in the printing ratio atthe respective splices.

the strips bein Recognizing the fact that the aforesaid variation in thecharacter of film emulsion can not be avoided in the manufacture ofcinematographic film on a commercial scale, the present invention aimsto annul or minimize the effect of such variation.

In one aspect the invention consists in synchronizing the variation inthe respective films so that corresponding portions of the separatelight sensitive films have substantially identical characteristics,whereby when the films are superposed the variations match and thebalance between the densities of the respective series of complementalimages remains substantially constant throughout the length of the film.Consequently if one series runs more or less dense throughout certainlengths of the film, the other series, runs correspondingly densethroughout the same lengths, so that the only effect is a change intotal density which results merely in a change in the brightness of thepicture without change in color cast.

I have found that the synchronization of the aforesaid variations may beefiected by coating the several strips which are to be employed inmaking the multi-ply color film with the same emulsion at the same time,fed through the coating process in para el juxtaposition so that cor-.responding portions of the respective films are coated undersubstantially identical conditions, the emulsion being applied to thefilm in any suitable way. At the coating stage of t e process therespective strips may be in the form of separate ribbons of celluloid orother suitable material of the requisite length, width and thickness orthey may be integrally joined in the form of a multi-width sheet. In thelatter case the multi-width sheet is slit to separate the strips beforethey are exposed. After the strips are separated they are rolled and therolls are matched, either by marking the ends or other portions of therespective films at points which were adjacent in the multiwidth sheetor if the extreme ends of the films were adjacent in the multi-widthsheet by merely rolling them with corresponding ends outermost, and thestrips are subsequently used in this matched relationship.

In building up the component strips or films by s licing sectionstogether, the respective s are spliced at corresponding points and thecorresponding sections are matched as herein described, whereby thecomponent films are matched throughout their entire lengths. Thus, it isunnecessary to change the printing ratio at the splices and inprojecting the finished pictures the color balance remains undisturbedat the splices.

So far as I am aware a set of separate fihns matched as aforesaid foruse in producing a color cinematographic film marks a distinct advancein the art and I therefore claim this product as a part of the presentinvention.

In practising the invention initially I have had the film matched by themanufacturer and shipped to the motion picture producer in matched form,but it is to be un- 'derstood that the film may be shipped in sheet formto be slit and matched by the producer prior to exposure.

While the various applications of the present invention in the use ofseparate films to produce a color film will be evident from theforegoing nevertheless for the purpose of illustration I have showndiagrammatically one application in the accompanying drawings in which,-

Fig. 1 indicates the stage of coating the mult1-width film;

Fig. 2 illustrates the step of slitting the multl-width sensitive film;

Fig. 3 represents a set of films matched accordin to the presentinvention;

Fi 4 indicates the step of perforating the mate ed films; and

Fig. 5, shows one way of exposing and uniting the films.

- Inasmuch as the steps of coating, slitting, perforating, exposing,etc., may be rformed in various ways and by different machines andinasmuch as the method here claimed involves the order of procedure, I

process of cementing before in the present have merely indicated thesteps of the method without attempting to show any details of thevarious machines employed.

The particular method of coating the film shown in Fig. 1 is of the typeemploying a drum, indicated at D, rotating over a tank, indicated at T,which contains the sensitive emulsion in liquid form, the multiwidthstrip S being fed over the drum in contact with the liquid.

The method of slitting the multi-width film shown in Fig. 2 comprisesfeeding the coated strip S ast a blade B, which divides the stri into apluralit of films F and F and t ence winding t e films into se aratereels R and R. While the multiwidth strip is shown as having the widthof only two films it may of course have a width such as to make anynumber of separate films.

In accordance with the cardinal feature of the invention involvin theuse of the films in matched relationshipthe films are preferably markedcorrespondingl Thus in Fig. 3 the edges of the matche films F and F arenotched at corresponding pointsM and M. The films are matched not onlylongitudinally but also transversely inasmuch as they were laterallyadjacent in the multi-width sheet.

The films thus matched are preferably perforated as shown in Fig. 4where the lms are fed together through a perforator, indicated at P, inthe matched relationship in which they are to be subsequently joinedtogether, thereby insuring. accurate registration of the perforations inthe respective films when joined together.

Fi 5 illustrates one method of exposing t e matched films whichcomprises feeding the films into parallel juxtaposition with negativefilms N and N having complemental series of negatives respectively,simultaneously exposing the positive films, and thence feeding the filmstogether through a cementing machine C where the films are cementedtogether back-to-back. With the emulsions on the outside the inulti-plyfilm may be carried through the developing and coloring processsubsequently to the cementing, thereby avoiding unequal shrinkage of thecomponent films in the wet treatments inasmuch as they are fast to ther.This eveloping is described and claimed in copending application SerialNo. 512,398, filed November 2, 1921 A cementing machine suitable for userocess'is' described and claimed in 00 en ing application Serial No.500,842, filed k eptember 15, 1921.

From the foregoing it is evident that the essence of the inventionconsists in a set of light-sensitive cinematographic films separatedfrom each other for separate exposure and other manipulation butrelatively matched so that variations throughout the lengths thereofrespectively are synchronized, and also in the production of a.composite color film by thus matching the separate component films, thenexposing the sepance lies in the point-to-point variation of theemulsion of the respective component films.

It is also evident that after the matched films are joined together inmatched relationship and before they are developed the composite filmconstitutes a double-coated film in which the variations of therespective coatings are synchronized or have corgisponding positionsalong the length of the The finished film is similarly unique in thatthe'variations in the density of the images of the respectivecomplemental series due to the aforesaid variations in the emulsionsfrom "which the images are formed have corresponding positions along thelength of the film.

I claim:

1. In the art of cinematography, the method of making multi-ply filmsfor color projection which comprises forming a multiwidth sensitivestrip, dividing the multiwidth strip into separate strips, subsequentlyforming complemental series of images on the separate stripsrespectively with the images of each complemental set on portions of theseparate strips which were adjacent in the multi-width strip, andjoining the separate strips together with the images which arecomplemental to each other in superposition prior to the liquidtreatment of the strips. is.

2.,Inthe art 6f cinematography, the method of making multi-plycinematographic films which comprises applying a. sensitive coating to amulti-width strip, dividing the multi-width strip into separate strips,subsequently forming complemental series of images on the separatestrips respectively-w th the images of each complemental set on portionsof the separate strips which were adjacent in the multi-width strip, theseparate strips being exposed .through their backs to form latent imagesadapted to be converted into direct relief, and subsequently joining theseparate strips together .with the images which are complemental to eachother in superposition.

3. In the art of cinematography, the method of making multi-ply filmsfor color projection which comprises forming a multi- Width sensitivestrip, dividing the multiwidth strip into separate strips, disposing thestrips in matchedesuperposed relationship, cutting the sprocket openingssimultaneously in both films while so disposed, forming complementalseries of images on the separate strips respectively with the images ofeach complemental set on the matched portions of the separate strips,and joining the strips together in, the said matched superposedrelationship with the images which are complemental to each other insuperposition.

4. In the art of cinematography, the method of making multi-ply filmsfor color projection which comprises forming a multiwidtlr sensitivestrip, dividing the multiwidth strip into separate strips, disposing thestrips in matched superposed relationship, cutting the sprocket openingssimultaneously in both films while so disposed, forming complementalseries of images on the separate strips respectively-with the images ofeach complementalset on the matched portions of the separate strips, andjoining the strips together back to back with the images which arecomplemental to each other in superpo- .sition.

5. In the art of cinematography, the method of making color films whichcomprises applying a sensitive coating to 'a multi-width strip, dividingthe multi-width strip into separate strips, mental series of images onthe separate strips respectively with the images of each complementalset on portions of the separate strips which were adjacent in themultiwidth strip, the separate strips bein exposed through their backsto form atent images adapted to be converted into direct reliefs, andemploying the se arate strips thus formed to produce a sing e=width filmhaving complemental images in registry.

6. In the art of cinematography, a set of separate emulsion-coated filmsmatched end for end, portions of the emulsions of the respective filmswhich have corresponding positions longitudinally of the films beingsubstantially identical and having thereon respectively mutuallycomplemental images of complemental series.

7. In the art of cinematography, the method of makin films for colorprojection which comprises orming a mult-i-width sensitive strip,dividing the multi-width strip into separate strips to provide separatelightsensitive films matched end for and, and forming complementalseries of images on the separate strips respectively with the mutuallycomplemental images of the comp1emental sets arranged in correspondingportions of the separate strips.

Signed by me at Boston, Massachusetts, this 31st day of December, 1921.

DANIEL F. COMSTOCK.

forming comple-

